Materials Chemistry Frontiers最新文献

Molybdenum disulfide (MoS₂) has great potential as an anode material for lithium-ion batteries due to its graphite-like layered structure and high specific capacity (669.0 mA h g⁻¹). However, challenges such as volume expansion during lithium storage have impeded its utilization. The combined alteration of MoS₂ and MXenes has demonstrated its efficacy as a modification technique. In this study, a green and facile phase engineering strategy has been implemented for the synthesis of MoS₂/Ti₃C₂T_x nanocomposites. Ti₃C₂T_x was rapidly prepared by the fluorine-free molten salt etching method, and then the MoS₂/Ti₃C₂T_x composite was synthesized by the one-pot method. Fluffy and open petal-like interconnect structures were constructed by combining few-layer MoS₂ nanosheets with Ti₃C₂T_x substrate. The introduction of the substrate material (Ti₃C₂T_x) provides a uniform growth platform for MoS₂ nanosheets, and Ti₃C₂T_x, acting as the supporting material, imparts enhanced structural stability to the composite. Theoretical calculations indicate that this configuration may result in a reduction of the diffusion energy barrier of Li⁺ from 0.78 eV to 0.19 eV, as well as an enhanced electron transfer. This composite material exhibits enhanced capacity performance, achieving 460.6 mA h g⁻¹ at 0.1 A g⁻¹ after 100 cycles. This approach offers valuable insights into the synthesis of additional high-performance composite materials.

In this study, we successfully upcycled a novel lignin-based covalent adaptable polyurethane elastomer (LPUE) that we previously synthesized into a graphene-composited covalent adaptable lignin-based polyurethane fabric (LPUF). This fabric exhibited outstanding solvent resistance, toughness (LPUF-0 with a tensile strength of 29.1 ± 1.6 MPa, an elongation at break of 653 ± 67%, and a toughness of 103 ± 3.8 mJ m⁻³), and deformation responsiveness. These results not only open up new possibilities for improving covalently adaptable networks in fabrics, but also pave the way for developing solvent-resistant, wearable sensing devices.

Cr³⁺-activated broadband near-infrared (NIR) phosphors usually show controllable and excellent photoluminescence (PL) properties, but their poor thermal stability remains a big challenge. Herein, a series of Lu_3−xCa_xGa_5−xSi_xO₁₂:Cr³⁺ garnet phosphors with tunable and abnormal thermal quenching performance have been successfully proposed. It is found that both the crystal field strength and calculated energetic difference between ⁴T₂ and ²E states decrease obviously with increasing [Ca²⁺–Si⁴⁺] co-substitution, resulting in the thermal occupation of the ⁴T₂ state and broadened PL spectra. More importantly, the Lu_3−xCa_xGa_5−xSi_xO₁₂:Cr³⁺ phosphors show improved PL thermal stability depending on the different thermal population between ⁴T₂ and ²E states, and the mechanism is investigated in detail. The PL intensity of the optimal sample reaches up to 125% and 121% at 425 K and 475 K compared with that at 300 K, respectively, which is much better than those of most Cr³⁺-activated broadband NIR phosphors. A NIR phosphor-converted light-emitting diode (NIR pc-LED) has been fabricated using the as-prepared thermally stable phosphor and its application in bio-imaging and night vision is demonstrated.

Piezochromic materials (PCMs) are highly valuable in advanced photonics and intelligent technologies. However, predicting piezochromic responses, a priori, in the design stage remains a formidable challenge. Herein, a novel series of PCMs, NICN-R (R = 1C, 2C, 3C and 4C), are designed and developed by incorporating naphthalimide (NI) and cyanostilbene (CN) with various alkoxyl chains (–R). Within a broad pressure range of ≈10 GPa, the initially synthesized NICNα-R molecules exhibit remarkable changes in the visible colors of photoluminescence emission. The pressure coefficients of emission shifts, ranging from 13.1 nm GPa⁻¹ to 16.3 nm GPa⁻¹, are considerably large in PCMs. To enhance the piezochromic effects, NICNβ-R molecules are further synthesized through regioselective cyanation. The pressure coefficients are obviously increased to 17.8–20.4 nm GPa⁻¹, attributed to the restrained molecular twisting and promoted intramolecular charge transfer. This study unveils the pivotal influence of the substitution position/length in molecular contraction and planarization under high pressure, which ultimately determines the piezochromic responses. It not only elucidates the mechanisms behind piezallochromy, but also proposes innovative design concepts for developing sensitive PCMs across broad pressure ranges.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a widely used electro-active conjugated polymer, is a good candidate for printed electronics owing to its advantages of solution processability and remarkable stability under oxygen conditions. However, achieving high conductivity is still a challenge in this field. Most previous studies have focused on the improvement of electrical conductivity of PEDOT via post-treatment of commercially available PEDOT:PSS. From another point of view, this work represents the enhancement in charge carrier transport by controlling polymerization parameters, i.e., oxidizing agent concentration and polymerization temperature. Thus, 2.25 equivalents of APS per mole of EDOT and 10 °C were found to be the optimum conditions. These produced PEDOT chains (with a low band gap energy, high oxidation state, quinoid structure and low molecular weights, along with the formation of enhanced fibrous PEDOT-rich domains in the solid state) enhanced electrical conductivity of the prepared PEDOT:PSS aqueous dispersion up to 165 S cm⁻¹. After solvent post-treatment of the optimum PEDOT:PSS dispersion, electrical conductivity increased up to 1410 S cm⁻¹, and this is the highest conductivity reported for post-treated PEDOT:PSS dispersions thus far. Finally, the obtained PEDOT:PSS dispersion was successfully formulated as a surfactant-free conductive ink for printing a three-layered circuit on a flexible substrate with a conductivity of 1800 S cm⁻¹ and lightening up an LED lamp using a direct ink writing (DIW) technique.

The need to switch to bio-based, biodegradable and/or fully recyclable polymers is becoming increasingly clear, especially in the area of food packaging, which is a major contributor to plastic pollution. To meet this challenge, biodegradable polymers must not only be economically viable, but also have properties that match or better those of conventional fossil-based polymers, such as robust mechanical strength and efficient gas barrier properties. One promising route is the production of composite materials from biodegradable polymers and SiO₂ nanoparticles. However, the high surface energy of SiO₂ often leads to agglomeration of the filler in the hydrophobic polymer matrix, which compromises the integrity of the composite. Here we present an innovative approach in which the surface of silica nanoparticles is modified with L-lactic acid oligomers (OLLA), effectively reducing the agglomeration of the filler and improving processability. Using conventional polymer processing methods that comply with industry standards, we prepared PLLA and PHBV nanocomposites and evaluated the effectiveness of the modification using a novel SBF-SEM technique. Our results show that modified silica achieves better dispersion in the polymer matrix and yields 70% more independent particles in the nanocomposite. The introduction of OLLA-g-SiO₂ increases the oxygen barrier of PLLA by 38% while accelerating the biodegradation rate and improving the toughness of the eco-friendly nanocomposites. This innovative approach offers a sustainable solution that is set to revolutionise the landscape of green food packaging.

The regulation of organic microcrystals with different fluorescence and morphological behaviors is pivotal for their applications; however, it is still complex to implement. Herein, we present the facile preparation of tunable light-emitting ionic organic microcrystals by the in situ self-assembly of a non-emissive squaraine dye (SQH) with various amines (NH₂Et, NHEt₂, NEt₃) or NEt₄OH. These behaviors primarily arise from the activation of conjugation in the surprisingly unconjugated configuration of zwitterionic SQH, which forms anionic SQ⁻ accompanied by ammonium counter ion in the microcrystals. The fluorescence quantum yields of these ionic microcrystals ranged from 18.6% to 68.2%, along with a change from two-dimensional to one-dimensional morphology, which is closely associated with their distinct cation–anion arrangements. Notably, the SQ–NH₂Et₂ microcrystals exhibited reversible vapoluminescence behavior at room temperature, enabling easy cryptographic application.

We systematically investigated the properties of AsXBr/AsYBr ((X ≠ Y) = S, Se and Te) Janus heterostructures with the goal of tailoring their characteristics for advanced supercapacitor applications. To our knowledge, this is the first reported study on these Janus heterostructures, thus offering novel insights into their properties. By employing density functional theory (DFT), we uncovered crucial insights into these materials. Notably, we found reduced indirect band gaps of 1.39 eV for AsSBr/AsSeBr, 1.08 eV for AsSBr/AsTeBr, and 1.23 eV for AsSeBr/AsTeBr, indicating their potential for efficient charge storage. Mechanical stability was confirmed, with ultra-low Young's modulus values for all structures. Our exploration of chalcogenides’ interchange effect in supercapacitors leads to the discovery of remarkable maximum quantum capacitance values: 426.62 μF cm⁻² for AsSBr/AsSeBr, 430.12 μF cm⁻² for AsSBr/AsTeBr, and 536.86 μF cm⁻² for AsSeBr/AsTeBr, respectively. Furthermore, our investigation into surface charge dynamics suggested that these materials act as cathode-type electrodes, enhancing their suitability for supercapacitor configurations. To ensure dynamical stability, we conducted detailed analysis of the phonon dispersion curves of these Janus heterostructures. These curves revealed no imaginary frequencies in the Brillouin zone, confirming the dynamical stability of AsSBr/AsSeBr and AsSeBr/AsTeBr Janus heterostructures. Additionally, our exploration extended to the assessment of the thermal properties, including the Seebeck coefficient (S), electronic conductivity (σ), and thermal conductivity (κ), of all heterostructures. The results, obtained through this methodology, utilized the SIESTA code to compute overlaps between Bloch states and trial localized orbitals. Subsequently, we employed Wannier90 to generate maximally-localized Wannier functions (MLWFs), which served as the basis set for interpolating band structures and computing transport properties via the BoltzWann module.

Two organic small molecule hole transport materials, 5-((3,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)thieno[3,2-b]thiophen-2-yl)methylene)-3-ethyl-2-thioxothiazolidin-4-one (shortly named C3-D) and 5,5′-((3,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)thieno[3,2-b]thiophene-2,5-diyl)bis(methaneylylidene))bis(3-ethyl-2-thioxothiazolidin-4-one) (shortly named C3-S), are designed with rhodanine as the functional group and utilized in inverted planar perovskite solar cells (PSCs). With the functional group, both HTMs exhibit good mobility, matching HOMO/LUMO energy levels and excellent interactions with ITO and the perovskite layer, enhancing hole extraction, transport, and defect passivation in inverted PSCs. As a result, the device based-on C3-D presents a champion power conversion efficiency (PCE) of 21.50% with J_SC = 24.49 mA cm⁻², V_OC = 1.072 V, and FF = 81.9%, while the device based-on C3-S shows a PCE of 19.24% with J_SC = 23.11 mA cm⁻², V_OC = 1.065 V, and FF = 78.2%. Additionally, the C3-D-based device also demonstrates superior stability compared to C3-S, retaining over 85% of the initial value after being kept for 500 h at room temperature in ambient air at 35% relative humidity, and over 60% of the initial value after being kept for 500 h at 85 °C in a N₂ glovebox, respectively. These results far surpass the performance of devices based-on a non-functional HTM, TT-3,6-TPA, as reported in the literature (a PCE of 0.7% with J_SC = 2.90 mA cm⁻², V_OC = 0.95 V, and FF = 27.0%). Therefore, these findings indicate that combining hetero-atomic functionalized groups with typical hole transport fragments could be a promising research avenue for enhancing the performance of inverted planar PSCs and facilitating the commercialization of perovskite solar cells.

Based on the terrible situation of energy shortage and environmental pollution, the research and development of multifunctional electrochemical materials for application in the field of renewable, pollution-free, and effective energy conversion and storage is currently a hot topic. It is worth noting that the hybridization of organic and inorganic materials can not only alleviate the poor electrical conductivity of organic materials but also prevent the aggregation and oxidation of inorganic materials, which is beneficial for the electrochemical process. Herein, a series of multifunction organic–inorganic hybrids have been successfully prepared through in situ polymerization of COF-TpDb nanolayers on the surface of Ti₃C₂T_x MXene sheets, followed by post-functionalization of the composites. Among these hybrids, the MX@COF-TpDb modified S-cathode exhibits higher initial specific capacity and better cycle durability than pure COF-TpDb in lithium–sulfur (Li–S) batteries, which is mainly due to the intervention of MXene that accelerates Li⁺ diffusion. Furthermore, the working electrode assembled with Fe/Co-MX@COF-TpDb-AO demonstrates the lowest overpotential compared to other metal coordination hybrids, which is primarily attributed to the synergistic effect of iron and cobalt ions that facilitates the electrocatalytic oxygen evolution process. Equally important, Co-MX@COF-TpDb-AO shows an electrocatalytic oxygen reduction pathway close to 4e⁻ and low H₂O₂ yield, which is comparable to most discovered COF-containing materials. Therefore, the idea of constructing MXene/COF hybrids sheds some light on the exploration of multifunctional electrochemical materials.